Energy companies triggered quakes, study says

Injecting carbon dioxide underground can trigger a troubling side effect

This map shows levels of CO2 in the part of the atmosphere where most weather occurs. Lighter colors indicate higher levels (up to 402 parts per million) while darker colors indicate lower levels (down to 391 parts per million). Data used to create this map were recorded in May 2013. At that time, CO2 was at its highest level in 800,000 years.

Scientists are scrambling to find a way to slow down or stop global warming. Many are tackling the problem by looking for ways to manage carbon dioxide, also known as CO2. Released by the burning of fossil fuels — such as oil, natural gas and coal — this pollutant traps heat near the planet’s surface. Some engineers propose injecting CO2 underground to keep it out of the atmosphere. Like a global Band-Aid, this could put off hot-planet problems for a while. But new data suggest it also might have a very troubling side effect: earthquakes.

Companies that drill for crude oil sometimes inject CO2 underground already. That CO2 helps them access buried pools of oil. But a new study has linked more than 100 earthquakes between 2006 and 2011 to CO2-injection wells in a Texas oil field. Most quakes were too small to be felt. Some, however, did produce low rumbles.

Cliff Frohlich, a geoscientist at the University of Texas at Austin, worked on the new study. He told Science News that it is “inconceivable that the injection wells weren’t contributing to these earthquakes.” He and coworker Wei Gan published their findings November 4 in the Proceedings of the National Academy of Sciences.

Scientists already knew that injecting fluids into the ground could cause quakes. The new study provides some of the first evidence that gas injections can do this too.

Frohlich says the new study doesn’t automatically rule out the idea of burying CO2. “This doesn’t mean it’s hugely dangerous,” he says. But he notes that this study, like a lot of science, “raises questions.”

One question is whether a well’s location affects its risk of triggering earthquakes. In the study, the authors note that nearby oil fields and other locations where CO2 had been injected underground have not experienced quakes.

“The really puzzling question is why some places and not others [are affected],” Emily Brodsky told Science News. A seismologist at the University of California, Santa Cruz, she did not work on the new study. But she and Frohlich agree that scientists need to conduct more studies to identify which mix of places and engineering practices leads to quakes.

That’s a difficult task, though, because oil companies tend to keep details about their drilling practices private. “We’re being asked to answer these questions but not always given the data to answer them,” Brodsky points out.

Power Words

carbon dioxide A gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. This colorless, odorless gas also is released when organic matter (including fossil fuels like oil or gas) is burned. Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere.

crude oil The term geologists use to describe petroleum as it comes out of the ground. Its consistency varies from place to place; it can be thin and pour easily or be thick like peanut butter.

earthquake A sudden and violent shaking of the ground, sometimes causing great destruction.

engineering The field of research that uses math and science to solve practical problems.

fossil fuels Any fuel (such as coal, oil or natural gas) that has developed in the Earth over millions of years from the decayed remains of bacteria, plant or animals.

geoscience Any of a number of sciences, like geology or atmospheric science, concerned with better understanding the planet.

global warming The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

seismology The science concerned with earthquakes and related phenomena. People who work in this field are known as seismologists.